Along
with the evolution of the metallic cartridge case and more efficient
propellants, some reliable method of igniting the package was required.
This is the job of the primer. Todays primers are essentially
a metallic cup containing an explosive mixture that serves to ignite
the main powder charge. The modern primer traces its history back
to the detonating powder developed in 1805 by Reverend
Alexander Forsyth. Forsyths compound utilized a mixture of
fulminate of mercury and potassium chlorate, offering a more convenient
and reliable alternative to the flintlock ignition system. This
was no small accomplishment, considering that the flintlock ignition
system had dominated the firearms world for over two hundred years.
Credit for the invention of the percussion cap is somewhat obscure,
with claims having been made by a long list of English, French,
German and Swiss experimenters. Joshua Shaw, an English born American
immigrant, is generally given credit for having developed the first
metallic percussion cap in 1814. Shaws percussion caps used
an explosive mixture of fulminate of mercury, chlorate of potash,
and ground glass contained in a small metallic cup. In use, this
cup was placed on a nipple beneath the firearms hammer. When the
trigger was pulled, the hammers blow caused the percussion
cap to detonate. This sent a jet of hot gases through a flash hole
in the nipple, igniting the primary charge of black powder, and
discharging the ball out the muzzle of the firearm. In a modern
cartridge, each of these different components is still present,
albeit in a single, self-contained unit. The percussion cap has
since become the primer. The nipple, originally part of the firearm,
is now located either in the case (Berdan) or the primer in the
form of the anvil (Boxer). The chamber walls, which held the powder,
have now been supplemented with a fixed cartridge case.

Boxer
or Berdan?

Today,
there are two basic priming systems in use worldwide for metallic
cased small arms ammunition. Designated as either Boxer or Berdan,
they are named after their respective designers. In a perverse quirk
of fate, thepriming
system used in England and throughout much of the rest of the world
was developed by an American, Col. Hiram Berdan. The predominant
priming system used here in the U.S. was invented by an English
ordnance officer, Col. Edward Boxer. The two systems are not at
all interchangeable, and must not be confused.

The
primary difference between the two is the placement of the anvil,
the point against which the priming compound is crushed. In the
Boxer system, the anvil is a separate piece affixed into the primers
cup, and bottoming out in the primer pocket when the primer is seated.
The Berdan system utilizes an integral anvil, formed into the base
of the primer pocket. Additionally, Boxer primed cases utilize a
single, fairly large, centrally located flash hole, making them
eminently suitable for reloading. Berdan primed cases, on the other
hand, normally have two or more smaller flash holes, located at
various points around the anvil. This makes it impossible to decap
Berdan cases as easily and efficiently as Boxer primed cases. While
Berdan brass can be reloaded, decap-ping the cases is much more
time consuming, and requires specialized equipment that is not commonly
available. Essentially, reloading Berdan cases is not worth the
effort if Boxer primed cases can be purchased or formed.

The
Berdan system has seen little use here in the U.S., and is rarely
encountered in anything but imported surplus foreign military ammunition.
One exception to this is the CCI Blazer® line of aluminum cased,
Berdan primed cartridges. In addition to their readily identifiable
aluminum cases, Blazer cases are prominently headstamped NR
to indicate their non-reloadable status. They should be discarded
after use, and never mixed with Boxer primed cases. Since Berdan
primers are little used and rarely encountered here in the U.S.,
all further references to primers will pertain to the Boxer type
primer unless otherwise noted.

Primer
Composition

One
ingredient that proved to be a great source of trouble in early
priming compounds was fulminate of mercury. Easy to manufacture
and very sensitive, fulminate of mercury was the basis for most
early percussion caps and primers. The real problems began when
brass cartridge cases and smokeless propellants began to see widespread
use. Upon firing, the mercury in the primer amalgamated with the
brass, chemically attacking and weakening the case. As long as black
powder was the primary propellant used in small arms ammunition,
this effect was minimized by the milder primers then in use, and
the lower operating pressures inherent to this type of propellant.
When smokeless propellants became more prevalent, the damage caused
by mercuric primers immediately began to create major difficulties.
While the mercury caused no damage to the firearm itself, cases
fired with this type of primer became brittle, rendering them useless
for further reloading. The damage was caused instantly upon firing,
could not be prevented, and could not be corrected afterwards. Mercury
was soon identified as the culprit, and was promptly eliminated.
Virtually all commercial primers have been made without fulminate
of mercury since around the turn of the century, and are still clearly
labeled as being non-mercuric. The U.S. military completely
suspended the use of mercuric primers around 1898, so the likelihood
of running into mercuric primers in anything other than extremely
old, or some foreign ammunition is remote.

Corrosion
was also a major problem in black powder firearms, due in part to
the nature of the propellant itself, but largely to the qualities
of the priming compound used in most early percussion caps and primers.
Potassium chlorate, used as an oxidizer, was a primary ingredient
in most of these mixes. Upon firing, some of this is deposited in
the bore in the form of potassium chloride. Being very similar to
ordinary table salt, potassium chloride is extremely hygroscopic,
which is to say it attracts and holds moisture.

Naturally,
this causes rusting in short order.

As
potassium chloride is soluble in water, but not by most conventional
bore solvents, its removal required very specific bore care techniques.
Since most bore solvents were not effective in dissolving or removing
this residue, some means of eliminating the potassium chlorate was
needed. Oddly enough, it took many years and some exhaustive studies
to determine what caused the gun corrosion problems experienced
in this period. It was not until 1922 that Dr. Wilbert J. Huff,
working for the Bureau of Mines at the request of the War Department,
identified chlorate primers as being the source of this corrosion.
Having located the agent causing the trouble, the next task was
to eliminate it by finding a substitute. This proved to be a long
and arduous task, despite the fact that rust-free primers were already
in use with several foreign military services around the world.
U.S. Ordnance was adamant concerning the reliability, storage life
and stability of any new compound used in their priming mixtures.
Their hesitancy to accept a new mixture was the result of a seemingly
minor change on the eve of World War One, which nearly had catastrophic
consequences. With U.S. troops already committed to combat in Europe,
Frankford Arsenal was forced to literally shut down its primer production
until the problem could be analyzed and corrected. After this experience,
they approached new developments with an understandable degree of
trepidation.

Eventually
a priming compound was developed that omitted the potassium chlorate,
using lead tri-nitro-resorcinate instead. Usually referred to as
lead styphnate, this is still a common oxidizer in many of todays
primers. This mixture proved to give the stability and reliability
demanded by the military, and was finally adopted after extensive
testing. On the commercial front, many American manufacturers were
already using noncorrosive primers in any of several different mixtures.
Corrosive primers may still be encountered, even though their use
was discontinued in U.S. commercial ammunition shortly after the
First World War. Foreign military surplus ammunition containing
corrosive primers (often of the Berdan type) is still frequently
found at discount prices. Considering the problems that may be associated
with its use, this ammunition may not be the bargain that it first
appears to be. In U.S. military ammunition, chlorate primers were
discontinued around 1950, but they may still be encountered in old
lots of .45 ACP and .30-06 rounds. The .30 Carbine was the first
U.S. martial cartridge that was loaded exclusively with noncorro-sive
primers. Later U.S. surplus ammunition in either 7.62mm NATO or
5.56mm NATO poses no problem in this regard.

Today,
small arms primers have evolved to the point of such extreme reliability
that they are often taken for granted. This is a mistake, as primer
selection and type can have a major effect on a given loads
accuracy and pressure. The components used in modern Boxer primers
consist of 1) a cup 2) the pellet, or priming mixture 3) the foil,
and 4) the anvil.

CUPS

Despite
their appearance, most primer cups are made of 70/30 cartridge brass.
Most manufacturers apply a nickel plating to their primers for appearance
sake, giving them their familiar silver coloration. The thickness
of the various types has a direct correlation on the strength and
sensitivity, largely determining whether it is suitable for a rifle
or pistol. The more thinly cupped pistol primer may not hold the
pressure of a high intensity rifle load, and may be pierced or blown
if used in this type of application. The thicker cups common to
rifle primers, on the other hand, may give misfires or accuracy
problems if they are used in some pistols. Despite the dimensional
similarities between the two types, they should not be interchanged.
There are some handgun cartridges that have been designed to use
rifle primers, such as the .221 Fireball, the 7mm TCU, and the .357
Remington Maximum. These, of course, should be used with the primers
for which they were originally intended. When using the reloading
data, please refer to the Test Components section for information
on which primer was used for our load development.

THE
PELLET

The
pellet is actual priming compound that is placed into the cup. As
we have seen, all modern primers are both noncorrosive, and non-mercuric.
Different amounts, and in some cases different types of priming
compound may be used, depending on primer make, size and type.

THE
FOIL

Made
of shellacked paper despite its name, the foil is a small circular
disc placed between the priming pellet and the anvil. This acts
as a shield for the pellet, protecting it from moisture and other
disruptive influences that may effect performance or reliability.
Some manufacturers color code this disc to aid in identification.
However, since there is no standard coding among manufacturers,
we recommend discarding any loose primers whose brand and or type
has become suspect.

THE
ANVIL

The
anvil in a boxer primer provides the hard point against which the
priming compound is crushed to detonate the primer. Like the cup,
these are generally made of 70/30-cartridge brass rolled into thin
sheets and punched into final shape. Most U.S. primers are of either
two or three-legged design, with the three legged design being by
far the most common. In examining a primer, you will note that the
anvil extends a few thousandths of an inch above the cup. This is
to allow the anvil to slightly compress the pellet when the primer
is seated, thus sensitizing the primer. These statements hold true
for both large and small sizes and for both rifle and pistol types.

PRIMER
SIZES AND TYPES

The
two predominate sizes of primers in use today fall into the basic
categories of small and large. These may
be further defined as being either rifle or pistol primers. Differences
between the two include priming composition mixture, cup thickness
and sensitivity, and very slight dimensional discrepancies in height.
Within these sub-categories, the primers are defined still further,
as standard, magnum, and in rifles, benchrest primers. Distinctions
between these types vary from brand to brand, but most relate to
composition mixtures, intensity and quality control standards during
production. Diameters of the two sizes are .175" for the small rifle
and pistol, and .210" for the large rifle and pistol, respectively.
With so many different sizes and types available, how does the reloader
know which type is appropriate for a given application? The following
paragraphs will serve as a general guide for primer selection. In
addition, the specific size, brand and type of primer used in our
data development is listed under the Test Components heading for
each cartridge in this manual.

SMALL
PRIMERS Small Pistol

Used
with most of the smaller handgun cartridges, from the .357 Magnum
down to the .25 ACP, when faster burning, easy to ignite powders
are being loaded. Small pistol primers, either standard or magnum,
must not be used for rifle cartridges. The higher operating pressures
common to these cartridges (even when used in a pistol, such as
the T/C Contender) presents a serious risk of pierced or blown primers
if the thin-cupped small pistol primers are substituted for the
correct rifle primer.

Examples:
Winchester WSP, Federal No.100

Small
Pistol Magnum

Small
Pistol Magnum primers are an appropriate choice for cartridges such
as the .357 Magnum when slow burning propellants are being used,
especially ball or spherical powders such as H110 or Winchester
296. They may also be a good choice for non-magnum cartridges when
extremely cold shooting conditions are encountered.

Examples:
CCI 550, Winchester WSPM

Small
Rifle

Although
they share the Small Pistol primers diameter (.175"), the
Small Rifle primers must not be randomly interchanged for pistol
loading. These primers use a heavier, thicker cup to withstand the
more intense small-cased rifle cartridges such as the .222 and .223
Remingtons. Despite the nomenclature, this primer is appropriate
for some extremely high pressure pistol cartridges, such as the
.221 Fireball and the .357 Maximum. They are also appropriate for
loading rifle cartridges such as the .223 Remington when using handguns
such as the XP-100 or T/C Contender.

Examples:
Remington 6 1/2, CCI 400

Small
Rifle Magnum

Providing
a hotter or more intense flame than a standard primer, the Small
Rifle Magnum is recommended for use with some ball powders, and
those loads that will be used in subzero temperatures. They may
also prove to be beneficial when very large amounts of powder are
being ignited, as in wildcats such as the .22 Cheetah.

Examples:
CCI 450, Federal 205

Small
Rifle Benchrest/Match

Made
with rigorous quality control standards, Small Rifle Benchrest/Match
primers may provide somewhat better accuracy than the standard Small
Rifle or Small Rifle Magnum primers. While this is not always the
case, it is usually worth experimenting with these primers if the
ultimate in accuracy is required.

Examples:
Remington 7 1/2, Federal 205M

LARGE
PRIMERS Large Pistol

Intended
for larger cases, such as the .45 ACP, .45 Colt, and 10mm Auto,
the large pistol primer shares the same thin-cupped design as its
smaller cousins. As such, large pistol primers present the same
risks as the small pistol primers if they are indiscriminately used
in rifle loads. Their use in rifles must be limited to those pistol
cartridges that have been chambered in rifle designs, such as the
.45 Colt in the Winchester M94 Trapper.

Examples:
CCI 300, Federal No.150

Large
Pistol Magnum

Large
Pistol Magnum primers offer the added power sometimes needed for
very large charges of slow burning pistol powders such as H110 and
Winchester 296. With their greater power, they may also be a good
choice for loads that will be used in subzero climates.

Examples:
Federal 155, CCI 350

Large
Rifle

Standard
Large Rifle primers are the correct choice for most rifle reloading
chores calling for the large primer. Adequate for all but the largest
and most difficult to ignite charges, standard Large Rifle primers
are probably the best choice for the vast majority of rifle reloading
applications. We suggest opting for the magnum primers only after
careful consideration of the type of cartridge being loaded, and
the circumstances under which the ammunition will be used. Remember,
the Magnum designation of a case does not necessarily
mean that it will require or even benefit from a magnum primer.

Examples:
Federal 210, Remington 9 1/2

Large
Rifle Magnum

Large
Rifle Magnum primers are made specifically for the larger charges
of very slow burning powders common to the bigger magnum rifle cartridges.
It is perhaps worth mentioning that some of this class of primers
have been developed for very specific applications. The Federal
215 primer, for example, was designed to reliably ignite the massive
powder charges associated with the Weatherby line of magnum cartridges.
These should be used as shown in the loading tables, and must not
be randomly substituted for standard large rifle primers. With their
sharper ignition characteristics, they will frequently give higher
pressures than a standard primer used in an otherwise identical
load. As is true with the Standard large rifle primers,
the Magnum designation does not necessarily preclude
the use of these primers in non-magnum cartridges, but the load
must be worked up again when primers are substituted.

Examples:
Federal 215, Remington 9 1/2 M

Large
Rifle Benchrest/Match

Large
Rifle Benchrest/Match primers, like the small rifle variety, may
offer improved accuracy in some load combinations. With the prospect
of improved accuracy, match-grade primers deserve some consideration
not only for competitive ammunition, but also for those hunting
applications that demand extreme accuracy.